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I have a Carrier furnace/ac. In December I replaced old manual thermostat with a Honeywell programmable one. No problems. Last month I called HVAC service to do spring checkup on AC and they found that the compressor was locked up. I bought house last year and still have home warranty, so had to go with a different vendor to get service. Anyway, after nearly a month, they finally came on Wednesday to install new compressor. Now I have a different problem. The unit runs continuously no matter what the temperature is set to.

If the temperature in the house is 75 and I crank the thermostat up to 90 and then turn to "cool" the AC turns on immediately. Same with heat. If I turn down to 50 and turn to "heat" furnace still comes on. It is not just the fan, but actual heat and cooling. Fan setting is set to Auto on the thermostat. The thermostat itself seems to be sensing the temperature correctly. If room temperature is above setting when on cool a little snowflake shows up on display panel, and if it is below setting when on heat a little flame shows up. But regardless, AC/heat kicks in.

We called back the AC company and they say it has to be a problem with the thermostat, but I have a hard time believing that this coincidentally just started happening after they came out. Could there be a setting on the HVAC unit itself that bypasses the temperature on the thermostat? It seems that this would be useful for servicing/diagnosing and I wonder if the serviceman just forgot to reset it. They agreed to come back next Wednesday to look. I am now manually turning on and off my programmable thermostat so I don't run continuously.

Thanks for any help.
 

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Sounds like they mau have shorted a wire during the replacement.

Call the warranty company. And have them send out either the same company, or another.
 
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